Brown fur seal description

The brown fur seal (Arctocephalus pusillus) is a large seal species of Australia and South Africa. The adult male brown fur seal has a light greyish-brown body and a dark brown belly, with a mane across the neck and shoulders which becomes lighter in colour with age. The female brown fur seal is browner than the male, but still has the darker brown belly (4). Pups are born black, and juveniles are generally the same colour as the female, but have lighter fur below the jaw and behind the ears (2)(4).

The head of the adult male brown fur seal is larger and broader than that of the female, and has a low brow, which is lacking in the female. Both sexes have a pointed snout, forward-facing nostrils, and moderately long whiskers which extend past the ears. The ears themselves are small and stick slightly out from the head (4). The paddle-shaped flippers of the brown fur seal are large and thick, and appear black when wet (5). The ability to turn the flippers forward helps distinguish fur seals from ‘true’ seals (species in the family Phocidae) (4).

The brown fur seal is split into two recognised subspecies, the Cape fur seal (Arctocephalus pusillus pusillus) and the Australian fur seal (Arctocephalus pusillus doriferus) (1). These two subspecies are genetically and behaviourally very similar, but occupy distinct ranges (1).

Related species

Brown fur seal biology

The brown fur seal feeds on pelagic schooling fish, such as pilchards, anchovies and hake, as well as cephalopods such as squid and octopuses, and also crustaceans. The brown fur seal has been known to dive to depths of up to 500 metres while foraging (2). Great white sharks (Carcharodon carcharias) and orcas (Orcinus orca) are known to prey on fur seals foraging out at sea, while the black-backed jackal (Canis mesomelas) and brown hyaena (Hyaena brunnea) also take pups while they are on land (1).

The male brown fur seal defends a territory with good resources to attract females (7). This species exhibits a ‘harem’ system in which one male mates with many females (8). Most seal and sea lion species mate on land; however, as brown fur seal females begin leaving on foraging trips before becoming receptive, some males follow the females out to sea, where they mate in the water (7).

The female brown fur seal becomes sexually mature at around the age of 3 years, but the male may not reach maturity until around 9 to 12 years. Breeding occurs from October the January, with births usually peaking in the first week of December. The female brown fur seal gives birth to a single pup after a gestation period of around one year (1). The brown fur seal pup measures about 60 to 80 centimetres at birth (2).

After giving birth, the female brown fur seal divides her time between attending the pup and foraging out at sea. The pup stays at the colony during this foraging time and survives off the milk it received during the female’s last visit. The female brown fur seal mates again just six days after giving birth, but continues to suckle her pup for up to 12 months (9). The male brown fur seal is known to live to at least 19 years of age, with females living to about 21 years (5).

Brown fur seal range

There are two geographically isolated populations of the brown fur seal. Colonies of the Cape fur seal (subspeciesA. p. pusillus) occur at sites along a 3,000 kilometre stretch of coastline from East London in the south-east of South Africa to southern Angola in the north-west. There are ten breeding colonies of the Cape fur seal: nine are on small, rocky islands near to the shore whereas the tenth is a large mainland colony which extends across three kilometres of coastline. There are also a large number of non-breeding colonies (6).

The Australian fur seal (subspeciesA. p. doriferus) is distributed across south-eastern Australia, from Port Stephens to islands around the Tasmanian coast and in Bass Strait. One colony has even been recorded on the mainland of Tasmania (4).

Species with a similar range

Brown fur seal habitat

The brown fur seal feeds out in the open sea but returns to land to breed and rest (2), usually using islands. It is also found on the mainland, though less frequently. This species generally prefers rocky sites (6).

Brown fur seal threats

At the height of the commercial sealing era between the 17th and 19th centuries, the brown fur seal was heavily over-harvested, as were many other closely related seal species. The sealing era ended in 1825, and the brown fur seal is now protected by law in most countries. However, although the numbers of brown fur seals are now increasing, seal harvesting still continues off the coast of Namibia (1).

As a marine species, the brown fur seal is venerable to oil spills and other forms of environmental damage (1). Pollution of the brown fur seal’s habitat with pesticides, heavy metals and noise disturbance is reported to be the one of the greatest threats this species faces (2). Both subspecies of the brown fur seal are also at risk from the introduction of diseases from land-based predators (1).

Fur seals are predators of fish, cephalopods and crustaceans, and because commercial fisheries also target these species, fur seals have learnt that fishing sites make good foraging areas (6). Brown fur seals have been observed taking fish from nets, and occasionally become tangled up and drown (2). There have also been reports of fur seals being shot illegally by fishermen to reduce competition for fish stocks (1).

Brown fur seal conservation

The brown fur seal is protected throughout all Australian states by the Environment Protection and Biodiversity Conservation Act (5). In South Africa, Cape fur seals (subspeciesA. p. pusillus) have been protected since 1893, but some authorized commercial harvesting still occurred until 1990 (10). In Namibia, the harvesting allowance and conservation of seals are now controlled by the Marine Resources Act, which aims to ensure a humane harvest (1).

International trade in the brown fur seal should be carefully regulated by its listing on Appendix II of the Convention on International Trade in Endangered Species (CITES) (5).

Glossary

Cephalopods

A group of marine molluscs with grasping tentacles and either an internal or external shell. Includes squids, octopuses, cuttlefish and nautiloids.

Crustaceans

Diverse group of animals with jointed limbs and a hard external skeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.

Gestation

The state of being pregnant; the period from conception to birth.

Pelagic

Relating to or inhabiting the open ocean.

Subspecies

A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Territory

An area occupied and defended by an animal, a pair of animals or a group.

Ride, W.D.L. (1970) A Guide to the Native Mammals of Australia. Oxford University Press, Oxford.

National Seal Strategy Group and Stewardson, C. (2007) National Assessment of Interactions between Humans and Seals: Fisheries, Aquaculture and Tourism. Australian Government Department of Agriculture, Fisheries and Forestry, Canberra.

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